Semigroups Congresses 2 Machine theory 2 Mathematics 2 Semigroup algebras 2 Algebra 1 Algebra, Universal 1 Algebraic varieties 1 Associative rings 1 Banach algebras 1 Decomposition 1 Finite groups 1 Fuzzy sets 1 History 1 Lattice theory 1 Markov processes 1 Matrices 1 Operator theory 1 Semirings (Mathematics) 1 Spectral theory (Mathematics) 1 Symmetry groups 1